An engine of a vehicle may be automatically stopped via a controller in response to vehicle operating conditions. For example, the engine may be stopped without the vehicle's driver specifically requesting an engine stop via an input that is dedicated to engine stopping and starting. The engine may be stopped to conserve fuel while the vehicle's driver (e.g., human or autonomous) waits for traffic conditions to clear or until the driver is ready to leave the vehicle's present location. The engine may be stopped while the vehicle's transmission is engaged in a gear, in neutral, or in park. If the vehicle is in a gear while the engine is stopped, the vehicle may be held in the gear by supplying hydraulic pressure to the transmission gear clutches via an electric pump. Similarly, at least some of the transmission's gear clutches may be engaged if the transmission is in neutral. By keeping one or more gear clutches engaged while the engine is stopped, engine torque may be transferred to the vehicle's wheels sooner after an engine restart because less fluid may have to be supplied to the transmission clutches. However, if the transmission is engaged in park, all gear clutches may have to be released. Consequently, if the engine is automatically restarted, significantly more transmission fluid may have to be delivered to the gear clutches before engine torque may be transferred to the vehicle's wheels. Having to supply larger amounts of fluid to engage transmission gear clutches after an automatic engine stop may delay when engine torque is available to the vehicle's wheels, thereby delaying vehicle launch. As such, it may be desirable to provide a way of reducing an amount of time it takes to fill transmission clutches of a vehicle that has an engine that has been automatically stopped while the vehicle's transmission is engaged in park.
The inventors herein have recognized the above-mentioned issues and have developed a vehicle operating method, comprising: automatically stopping an engine via a controller without receiving specific input from a driver via a dedicated engine start/stop input; and automatically starting the engine via the controller in response to applying a brake pedal while the engine is automatically stopped and a transmission is engaged in park.
By automatically starting an engine of a vehicle that has been automatically stopped in response to applying a brake pedal while the transmission is engaged in park, it may be possible to provide the technical result of reducing a delay in vehicle launch. In particular, the engine may be started before the driver shifts from park to drive so that the engine may rotate the pump within the transmission and increase the availability of fluid at the transmission's clutches before the transmission is shifted into gear. Conversely, if engine starting where delayed until the vehicle's driver moved a shifter from park to neutral, then the buildup of transmission fluid pressure would be delayed until shifter motion was detected. However, shifting the transmission from park into drive requires applying a brake pedal before shifter movement is allowed so that the possibility of vehicle motion may be reduced. Starting the engine in response to the earlier application of the brake pedal allows the engine to start and the transmission fluid pump output to increase before the shifter is moved, thereby decreasing an amount of time between when the shifter is moved and when torque is made available to vehicle wheels via pressurized fluid flowing from the transmission pump to the transmission gear clutches.
The present description may provide several advantages. In particular, the approach may reduce an amount of time between when a shifter is moved and engine torque is provided to vehicle wheels. Further, the approach may be applied to a variety of scenarios where a vehicle's transmission is engaged in park while the vehicle's engine is automatically stopped. Further still, variants of the approach may further improve the availability of transmission fluid to transmission clutches after an automatic engine stop in response to road conditions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.